Structural frames in vehicles are commonly assembled from a plurality of separate frame members of various cross sections including tubular members, I-beams and the like. The assembly of frames of various contours and shapes requires a complex arrangement of parts which are individually joined together so as to be costly and labour intensive to assemble.
U.S. Pat. No. 6,805,401 by Hayashi et al. discloses a vehicle floor structure in which a plurality of beam elements are assembled together and reinforced by continuous inner and outer flat sheets spanning the inner and outer sides of the frame respectively. The large number of beam elements formed with flanges at top and bottom edges thereof are limited in the shapes that can be formed due to the limitations of bending the flanges on the beam elements prior to assembly. The sheeted material which fully spans the inner and outer sides results in a large use of material even in places where minimal material is required for strength resulting in unnecessarily heavy construction which utilizes costly unnecessary material. Furthermore the beam elements require the extra top and bottom flanges thereof for support and attachment to the sheets so as to incur further costs for material not necessary for strength. Due to the continuously spanning nature of the inner and outer sheets, assembly requires all of the beam elements to be initially mounted onto one of the sheets for access to intermediate ones of the beam elements prior to any attachment of the second sheet. The assembly thus requires multiple steps of locating beam elements and subsequently welding the sheets separately from one another.